The present invention relates to cosmetic compositions, more particularly to solid cosmetic compositions, and especially to antiperspirant or deodorant compositions in the form of an emulsion.
Topically applied antiperspirant compositions are in widespread use throughout much of the world, in order to enable their users to avoid or minimise visible wet patches on their skin, especially in axillary regions. Antiperspirant formulations have been applied using a range of different applicators, including aerosols, roll-ons, pump sprays, sticks and mushroom applicators, in accordance with the individual preferences of consumers. In some parts of the world, sticks are especially popular. The term stick traditionally indicates a bar of solid material which was usually housed within a dispensing container and which retains its integrity whilst being applied, i.e. a firm stick. When a portion of a firm stick is drawn across the skin surface, a film of the stick composition is transferred onto the skin surface. Although the stick has the appearance of a solid article, the material forming the stick usually comprises a structured liquid phase such that a film of the material is readily transferred onto another surface upon contact under pressure. One class of stick which has been contemplated for antiperspirant or deodorant application comprises an emulsion stick. Such sticks comprise a continuous phase in which is dispersed droplets of a second liquid phase, normally referred to as a disperse phase. The continuous phase is one of hydrophobic or aqueous, and the disperse phase constitutes the other. The antiperspirant or deodorant active is conveniently incorporated within the aqueous phase. The hydrophobic phase can be structured by incorporation of wax structurants, these being materials which typically are solid at ambient temperatures, but which melt or dissolve or disperse into the oils constituting the hydrophobic phase at elevated temperatures, for example selected between 60 and 120xc2x0 C., depending on the choice of oil and wax. When the mixture of wax structurant and oil cools to below its setting temperature, the oil phase solidifies.
When formulating emulsion sticks, there are a number of factors to be taken into account. Some of the factors are antagonistic. One of the first and very important factors relates to the respective proportions of the two phases. The antiperspirant salts have finite solubility in the aqueous phase, so that antiperspirant efficacy potentially increases as the proportion of the aqueous phase increases. However, any increase in the proportion of aqueous phase in the formulation results in a corresponding decrease in the space available to the hydrophobic phase. In conjunction with the choice of its constituent oil or oils, this affects the ability of the hydrophobic phase to provide a strong supporting continuous phase, and hence the strength and integrity of the stick. Moreover, it affects the ability of that phase to contain beneficial hydrophobic constituents.
Waxes have been commonly used or proposed for use in structuring anhydrous formulations, in which a particulate antiperspirant is suspended in an oil phase, but much less attention has been given to their use to structure emulsion sticks.
The market for underarm products is constantly evolving as consumers"" tastes and lifestyles change. One attribute of underarm formulations to which consumers have paid considerable attention in recent years is the extent to which the formulation is visible on the skin, either shortly after application or subsequently throughout the following day. This is commonly referred to as visible deposits. Waxes and antiperspirant salts can give rise to visible deposits on human skin, so that in line with current consumer preferences, it would be desirable to be able to reduce or ideally eliminate them. A related attribute relates to the visibility of the formulation on any clothing, either occurring in the course of its application to the skin or by subsequent transfer by contact of the skin with the clothing. Likewise, it would be desirable to reduce or ideally eliminate visible deposits on clothing.
Some oils are effective carriers for distributing antiperspirant or deodorant actives on the skin, but have little effect on visible deposits. Various other oils can ameliorate the appearance of visible deposits, but the space available for such oils in emulsions is constrained by the proportion occupied by the aqueous phase.
The effect of the oils on the ease with which a firm emulsion stick can be formulated has been mentioned herein before. A further factor relates to the variation in sensory attribute of emulsion sticks made using different oils. Thus, for example, such formulations can have a high drag on passage across the skin or they can show a filmy deposit on the skin. They can appear to be sticky when in the dispensing container or on application to the skin, or they feel greasy.
The prior art contains various publications disclosing sticks containing an aqueous component. Thus, for example U.S. Pat. No. 4,265,878 exemplifies a formulation containing substantially no non-volatile oil. The formulation exhibits high visible deposits. U.S. Pat. No. 5,162,378 discloses emulsions containing an aqueous phase, but without a non-volatile oil. Like ""878, it provides no teaching on the problems associated with formulations containing non-volatile oils and how to solve them. U.S. Pat. No. 4,704,271 discloses formulations containing a high proportion of disperse aqueous phase, a continuous phase containing a low proportion of non-volatile oil and a high ratio of volatile to non-volatile oils, structured with stearyl alcohol. This formulation has an intrinsically high level of visible deposits from its active and structurant which is reduced to only a limited extent.
WO 98/17238 exemplifies emulsion formulations containing non-volatile oils that are free from volatile silicones. Consequently, it is silent as to the constraints relating to formulations, which desire to contain both such constituents and the benefits from containing both of them in selected proportions.
EP-A-0291334 circumvents the use of waxes by employing a liquid crystal phase to structure the product. Accordingly, it provides no teaching concerning the provision of wax-structured structured emulsions containing both a volatile silicone and a non-volatile oil.
EP-A-0281288 exemplifies an antiperspirant formulation in which an oil phase containing only a small proportion of a non-volatile oil is structured with stearyl alcohol. Such a formulation exhibits a high drag and indeed also has a relatively high visible deposit. Accordingly, it does not provide teaching on how to address such issues. EP-A-0295071 discloses emulsion sticks employing a disperse phase based on a polyhydric alcohol, which can also contain a minor proportion of water. Propylene glycol is exemplified in a 4:1 weight ratio to water in the disperse phase. Sticks which are based on propylene glycol as the principal lipophobic constituent typically exhibit stickiness.
It is an object of the present invention to provide an emulsion stick formulated to exhibit a desirable combination of sensory attributes, stick integrity and reduction of visible deposits.
According to one aspect of the present invention there is provided a cosmetic composition in the form of a stick containing an antiperspirant or deodorant active and comprising a continuous hydrophobic phase containing a volatile silicone oil, a non-volatile hydrophobic oil and a wax structurant, a disperse aqueous phase and an emulsifier characterised in that the continuous phase comprises from 10 to 35% volatile silicone oil, and from 5 to 15% non-volatile hydrophobic oil, the disperse phase comprises from 40 to 75%, the antiperspirant or deodorant active comprises from 1 to 35%, the wax structurant comprises from 7 to 25%, the emulsifier comprises from 0.1 to 10%, and the composition preferably contains up to 5% insoluble particulate materials, %s being by weight based on the composition.
By the employment of a composition of constituents selected within the ranges specified hereinabove, it is possible to produce an antiperspirant or deodorant emulsion stick exhibiting a combination of two or more beneficial properties, from the list of avoiding or ameliorating visible deposits, avoiding or ameliorating filmy deposits, avoiding or ameliorating drag, avoiding or ameliorating stickiness, and improving or retaining consumer-acceptable glide, whilst continuing to enjoy an acceptable stick hardness. In other words, it is possible to produce a stick from an emulsion, which is structured using a wax, and which exhibits a number of attributes which are well liked by consumers.
In a related aspect of the present invention, there is provided a process for making the compositions of the first aspect, namely, comprising the steps of forming a hydrophobic mixture by mixing a volatile silicone oil, a non-volatile oil and a wax structurant at an elevated temperature or bringing the mixture to the elevated temperature at which the structurant melts or is dissolved or dispersed in the oils, thereby forming a mobile hydrophobic mixture, simultaneously or sequentially forming an aqueous phase containing water soluble or miscible constituents, shear mixing the mobile hydrophobic mixture with the aqueous phase in the presence of an emulsifier, and any insoluble particulate materials thereby forming an emulsion comprising a hydrophobic continuous phase and a disperse aqueous phase, cooling or permitting the emulsion to cool to a temperature at which a solid is formed by the structurant structuring the continuous phase, characterised in that the continuous phase comprises from 10 to 35% volatile silicone oil, and from 5 to 15% non-volatile hydrophobic oil, the disperse phase comprises from 40 to 75%, the antiperspirant or deodorant active comprises from 0.5 to 35%, the wax structurant comprises from 7 to 25%, the emulsifier comprises from 0.1 to 10%, the composition preferably contains up to 5% insoluble particulate materials, %s being by weight based on the composition.
In a further related aspect of the present invention, the compositions according to the first aspect or made according to the second aspect are applied topically to the skin in order to reduce or prevent perspiration or body odor. Specifically there is provided a method for preventing or reducing perspiration or odors on human skin and particularly in armpits comprising applying topically to the skin an emulsion in the form of a stick containing an antiperspirant or deodorant active comprising a continuous hydrophobic phase containing a volatile silicone oil a non-volatile hydrophobic oil and a wax structurant, a disperse aqueous phase and an emulsifier characterised in that the continuous phase comprises from 10 to 35% volatile silicone oil, and from 5 to 15% non-volatile hydrophobic oil, the disperse phase comprises from 40 to 75%, the antiperspirant or deodorant active comprises from 1 to 35%, the wax structurant comprises from 7 to 25%, the emulsifier comprises from 0.1 to 10%, the composition preferably contains up to 5% insoluble particulate materials, %s being by weight based on the composition.